from flask import Flask, jsonify, request
import hashlib
import requests
import json
from time import time
from uuid import uuid4
from urllib.parse import urlparse


class Blockchain(object):
    def __init__(self):
        self.nodes = set()
        self.chain = []
        self.current_transactions = []
        self.new_block(proof=100, previous_hash=1)  # 创建创世块

    '''
    生成新块
    :param proof: <int> The proof given by the Proof of Work algorithm
    :param previous_hash: (Optional) <str> Hash of previous Block
    :return: <dict> New Block
    '''
    def new_block(self, proof, previous_hash=None):
        block = {
            "index": len(self.chain) + 1,
            "timestamp": time(),
            "transactions": self.current_transactions,
            "proof": proof,
            "previous_hash": previous_hash or self.hash(self.chain[-1]),
        }
        # Reset the current list of transactions
        self.current_transactions = []
        self.chain.append(block)
        return block

    '''
    生成新交易信息，信息将加入到下一个待挖的区块中
    :param sender: <str> Address of the Sender
    :param recipient: <str> Address of the Recipient
    :param amount: <int> Amount
    :return: <int> The index of the Block that will hold this transaction
    '''
    def new_transaction(self, sender, recipient, amount):
        self.current_transactions.append({
            "sender": sender,
            "recipient": recipient,
            "amount": amount,
        })
        return self.last_block["index"] + 1

    '''
    生成块的 SHA-256 hash值
    '''

    @staticmethod
    def hash(block):
        # We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
        block_string = json.dumps(block, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

    @property
    def last_block(self):
        return self.chain[-1]

    '''
    简单的工作量证明:
    查找一个 p' 使得 hash(pp') 以4个0开头
    p 是上一个块的证明,  p' 是当前的证明
    :param last_proof: <int>
    :return: <int>
    '''
    def proof_of_work(self, last_proof):
        proof = 0
        while self.valid_proof(last_proof, proof) is False:
            proof += 1
        return proof

    @staticmethod
    def valid_proof(last_proof, proof):
        tmp_str = str(last_proof) + str(proof)
        guess = tmp_str.encode()
        guess_hash = hashlib.sha256(guess).hexdigest()
        print(guess_hash, len(guess_hash))
        return guess_hash[:4] == "0000"

    '''
    Add a new node to the list of nodes
    :param address: <str> Address of node. Eg. 'http://192.168.0.5:5000'
    :return: None
    '''
    def register_node(self, address: str):
        parsed_url = urlparse(address)
        self.nodes.add(parsed_url.netloc)

    '''
    检查是否是有效链，遍历每个块验证hash和proof
    '''
    def valid_chain(self, chain):
        last_block = chain[0]
        current_index = 1
        while current_index < len(chain):
            block = chain[current_index]
            print(last_block)
            print(block)
            print("\n-----------\n")
            # Check that the hash of the block is correct
            if block['previous_hash'] != self.hash(last_block):
                return False
            # Check that the Proof of Work is correct
            if not self.valid_proof(last_block['proof'], block['proof']):
                return False
            last_block = block
            current_index += 1
        return True

    '''
    共识算法解决冲突
    使用网络中最长的链.
    :return: <bool> True 如果链被取代, 否则为False
    '''
    def resolve_conflicts(self):
        neighbours = self.nodes
        new_chain = None
        # We're only looking for chains longer than ours
        max_length = len(self.chain)
        # Grab and verify the chains from all the nodes in our network
        for node in neighbours:
            response = requests.get('http://' + str(node) + '/chain')
            if response.status_code == 200:
                length = response.json()['length']
                chain = response.json()['chain']
                # Check if the length is longer and the chain is valid
                if length > max_length and self.valid_chain(chain):
                    max_length = length
                    new_chain = chain
        # Replace our chain if we discovered a new, valid chain longer than ours
        if new_chain:
            self.chain = new_chain
            return True
        return False


app = Flask(__name__)
node_identifier = str(uuid4()).replace('-', '')
# Instantiate the Blockchain
blockchain = Blockchain()


@app.route('/')
def hello_world():
    return 'Hello World!'


'''
计算工作量证明PoW
通过新增一个交易授予矿工（自己）一个币
构造新区块并将其添加到链中
'''


@app.route('/mine', methods=['GET'])
def mine():
    # We run the proof of work algorithm to get the next proof...
    last_block = blockchain.last_block
    last_proof = last_block['proof']
    proof = blockchain.proof_of_work(last_proof)
    # 给工作量证明的节点提供奖励.
    # 发送者为 "0" 表明是新挖出的币
    blockchain.new_transaction(
        sender="0",
        recipient=node_identifier,
        amount=1,
    )
    # Forge the new Block by adding it to the chain
    block = blockchain.new_block(proof)
    response = {
        'message': "New Block Forged",
        'index': block['index'],
        'transactions': block['transactions'],
        'proof': block['proof'],
        'previous_hash': block['previous_hash'],
    }
    return jsonify(response), 200


@app.route('/transactions/new', methods=['POST'])
def new_transaction():
    values = request.get_json()
    # Check that the required fields are in the POST'ed data
    required = ['sender', 'recipient', 'amount']
    if not all(k in values for k in required):
        return 'Missing values', 400
    # Create a new Transaction
    index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])
    response = {'message': 'Transaction will be added to Block ' + str(index)}
    return jsonify(response), 201


@app.route('/chain', methods=['GET'])
def full_chain():
    response = {
        'chain': blockchain.chain,
        'length': len(blockchain.chain),
    }
    return jsonify(response), 200


@app.route('/nodes/register', methods=['POST'])
def register_nodes():
    values = request.get_json()
    nodes = values.get('nodes')
    if nodes is None:
        return "Error: Please supply a valid list of nodes", 400
    for node in nodes:
        blockchain.register_node(node)
    response = {
        'message': 'New nodes have been added',
        'total_nodes': list(blockchain.nodes),
    }
    return jsonify(response), 201


@app.route('/nodes/resolve', methods=['GET'])
def consensus():
    replaced = blockchain.resolve_conflicts()
    if replaced:
        response = {
            'message': 'Our chain was replaced',
            'new_chain': blockchain.chain
        }
    else:
        response = {
            'message': 'Our chain is authoritative',
            'chain': blockchain.chain
        }
    return jsonify(response), 200


if __name__ == '__main__':
    from argparse import ArgumentParser

    parser = ArgumentParser()
    parser.add_argument('-p', '--port', default=5000, type=int, help='port to listen on')
    args = parser.parse_args()
    port = args.port

    app.run(host='127.0.0.1', port=port)
